London: The London Marathon runners fell silent at the start line on Monday in memory of those who died in the Boston bomb attacks. (Agencies)
Amid tightened security to reassure the racers and crowd, there was a 30-second silence just before the start of the men's elite race and mass start at 10am.
Many of the 36,000 fun-runners, athletes and fundraisers wore black ribbons in a show of solidarity with those affected by the terror attacks at the finish of the Boston Marathon last Monday. Three people were killed and 180 injured in the Massachusetts blasts.
Virgin London Marathon has pledged to donate 2 pound sterling for every finisher in today's event to the One Fund Boston set up to raise money for victims of the explosions.
Organizers have stressed that as well as showing defiance and spirit in the showpiece event, the participants will have fun around the famous 26.2-mile course.
Geoff Wightman, the event commentator, announced over loudspeakers before the half-minute silence: "Marathon-running is a global sport. It unites runners and supporters on every continent in pursuit of a common challenge and in the spirit of friendship and fellowship.
"This week the world marathon family was shocked and saddened by the events at the Boston Marathon. In a few moments a whistle will sound and we will join together in silence to remember our friends and colleagues for whom a day of joy turned into a day of sadness.
"Let us now show our respect and support for the victims of the tragedy in Boston." The silence appeared to be perfectly observed.
Earlier, former director of the London Marathon David Bedford told the BBC: "We've had a fantastic response from our runners. There were many calls – please carry on, please run the race."
London: The London Marathon runners fell silent at the start line on Monday in memory of those who died in the Boston bomb attacks.